<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    #app1 {
      width: 250px;
      height: 250px;
      background-color: #c4b7d7;
      margin: 40px auto;
      display: inline-block;
    }

    #app2 {
      display: inline-block;
      margin: 0 auto;
      width: 0;
      height: 0;
      border: 125px solid;
      border-top-color: springgreen;
      border-left-color: #c4b7d7;
      border-right-color: transparent;
      border-bottom-color: steelblue;
    }

    #app3 {
      display: inline-block;
      width: 0;
      height: 0;
      border-top: 125px solid antiquewhite;
    }
  </style>
</head>

<body>
  <div>
    <div id="app1"></div>
    <div id="app2"></div>
    <div id="app3">啥也没有</div>
  </div>
</body>

</html>